title: Facilitation as a ubiquitous driver of biodiversity.
abstract: Models describing the biotic drivers that create and maintain biological diversity within trophic levels have focused primarily on negative interactions (i.e. competition), leaving marginal room for positive interactions (i.e. facilitation). We show facilitation to be a ubiquitous driver of biodiversity by first noting that all species use resources and thus change the local biotic or abiotic conditions, altering the available multidimensional niches. This can cause a shift in local species composition, which can cause an increase in beta, and sometimes alpha, diversity. We show that these increases are ubiquitous across ecosystems. These positive effects on diversity occur via a broad host of disparate direct and indirect mechanisms. We identify and unify several of these facilitative mechanisms and discuss why it has been easy to underappreciate the importance of facilitation. We show that net positive effects have a long history of being considered ecologically or evolutionarily unstable, and we present recent evidence of its potential stability. Facilitation goes well beyond the common case of stress amelioration and it probably gains importance as community complexity increases. While biodiversity is, in part, created by species exploiting many niches, many niches are available to exploit only because species create them.
authors.affiliation: Canadian Forest Service, Natural Resources Canada, 506 Burnside Road W., Victoria, BC, Canada, V8Z 1M5.|Canada Research Chair - Conservation Biology and Modeling, Département des sciences du bois et de la forêt, Université Laval, Québec, QC, Canada.
authors.forename: Eliot J B
authors.initials: EJB
authors.lastname: McIntire
authors.affiliation: Centro de Investigación en Ecosistemas de la Patagonia (CIEP) Conicyt-Regional R10C1003, Universidad Austral de Chile, Ignacio Serrano 509, Coyhaique, Chile.
authors.forename: Alex
authors.initials: A
authors.lastname: Fajardo
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D003247:Conservation of Natural Resources; D017753:Ecosystem; D020387:Food Chain; D008954:Models, Biological; D011157:Population Dynamics; D012932:Social Facilitation; D013312:Stress, Physiological
keywords: biodiversity; coexistence; facilitation; intransitive competition; plant functional traits; positive interactions; resource sharing; stress gradient hypothesis (SGH)